Romantic relationships are central in adolescents'social lives and emotional experiences, and have important implications for socio-emotional adjustment and mental health. During the current funding period of this grant (RO1-MH50106), we have been examining the pattern of relations among adolescents'romantic relationships, their other close relationships, sexual activity, substance use, and mental health. We have been following a sample of 200 adolescents who were recruited in the 10th grade and will be seen for 4 years (with 99+ percent retention after 3 years). Observations, interviews, and questionnaires are gathered from the adolescents. Their parents, friends, and partners also provide information about their relationships and mental health. Consistent with our theoretical model and the grant's aims, we have found: a) developmental changes in these relationships, b) links with other close relationships, and c) evidence that romantic experiences may both promote healthy adjustment and be linked to problems in mental health, including risky sexual behavior, depression and other internalizing symptoms, externalizing symptoms, and substance use. This application is for a competing continuation to examine the course of their romantic experience in the period of emerging adulthood. Using the same multi-method, multi-agent approach as in the prior waves, we propose to gather three additional assessments spaced 18 months apart. Major new aims are: 1) to examine development, continuity, and change in romantic relationships and experience from adolescence into and during the critical period of emerging adulthood, 2) to determine the degree to which past romantic experience and experiences in other close relationships are predictive of romantic experience in the emerging adulthood years and, 3) to determine the degree to which romantic experiences are predictive of adjustment and mental health problems in the emerging adulthood years as well as how adjustment and mental health problems are predictive of problematic romantic experience in merging adulthood. The findings will contribute both to basic theories of psychosocial development and to prevention science.